Antibacterial, Resistance Modulation, Anti-Biofilm Formation, and Efflux Pump Inhibition Properties of Loeseneriella africana (Willd.) N. Halle (Celastraceae) Stem Extract and Its Constituents

This study investigated the antibacterial, resistance modulation, biofilm inhibition, and efflux pump inhibition potentials of Loeseneriella africana stem extract and its constituents. The antimicrobial activity was investigated by the high-throughput spot culture growth inhibition (HT-SPOTi) and broth microdilution assays. The resistance modulation activity was investigated using the anti-biofilm formation and efflux pump inhibition assays. Purification of the extract was carried out by chromatographic methods, and the isolated compounds were characterized based on nuclear magnetic resonance, Fourier transform infrared and mass spectrometry spectral data and comparison with published literature. The whole extract, methanol, ethyl acetate, and pet-ether fractions of L. africana all showed antibacterial activity against the test bacteria with MICs ranging from 62.5 to 500.0 µg/mL The whole extract demonstrated resistance modulation effect through strong biofilm inhibition and efflux pump inhibition activities against S. aureus ATCC 25923, E. coli ATCC 25922 and P. aeruginosa ATCC 27853. Chromatographic fractionation of the ethyl acetate fraction resulted in the isolation of a triterpenoid (4S,4αS,6αR,6βS,8αS,12αS,12βR,14αS,14βR)-4,4α,6β,8α,11,11,12β,14α-Octamethyloctadecahydropicene-1,3(2H,4H)-dione) and a phytosterol (β-sitosterol). These compounds showed antibacterial activity against susceptible bacteria at a MIC range of 31-125 µg/mL and potentiated the antibacterial activity of amoxicillin (at ¼ MIC of compounds) against E. coli and P. aeruginosa with modulation factors of 32 and 10, respectively. These compounds also demonstrated good anti-biofilm formation effect at a concentration range of 3-100 µg/mL, and bacterial efflux pump inhibition activity at ½ MIC and ¼ MIC against E. coli and P. aeruginosa. Loeseneriella africana stem bark extracts and constituents elicit considerable antibacterial, resistance modulation, and biofilm and efflux pump inhibition activities. The results justify the indigenous uses of L. africana for managing microbial infections.

Modulating Effects of the Hydroethanolic Leaf Extract of Persicaria lanigera R. Br. Soják (Polygonaceae) against Acute Inflammation

Plant species have been used traditionally to treat numerous inflammatory disorders because of their known medicinal properties. This study aimed to assess the anti-inflammatory effect of aqueous ethanolic leaf extract of Persicaria lanigera using acute inflammatory models. The safety profile of the Persicaria lanigera extract was assessed using an acute toxicity model. The anti-inflammatory effect of the Persicaria lanigera leaf extract (100-600 mg·kg^-1, p.o.) was studied in carrageenan-induced paw oedema, zymosan-induced knee joint arthritis, and histamine-induced paw oedema in Sprague-Dawley rats (n = 5). It was observed that the Persicaria lanigera leaf extract administered prophylactically significantly inhibited paw oedema from 99.01 ± 12.59 to 59.10 ± 4.94%, 56.08 ± 3.65%, and 48.62 ± 3.27% at 100 mg·kg^-1, 300 mg·kg^-1, and 600 mg·kg^-1, while the standard drug, aspirin, showed 41.84 ± 9.25% in carrageenan-induced paw oedema, respectively. Furthermore, the extract decreased knee joint inflammation significantly from 62.43 ± 5.73% to 32.07 ± 2.98% and 24.33 ± 8.58% at 300 mg·kg^-1 and 600 mg·kg^-1 in zymosan-induced knee joint inflammation, respectively. In the histamine-induced paw oedema model, the extract significantly inhibited oedema to 61.53 ± 9.17%, 54.21 ± 9.38%, and 54.22 ± 9.37% at the same doses. Aqueous ethanolic leaf extract of Persicaria lanigera is safe and attenuates inflammation in acute inflammation models.

Phenotypic and Genomic Insights into Biofilm Formation in Antibiotic-Resistant Clinical Coagulase-Negative Staphylococcus Species from South Africa

The work aims to investigate biofilm formation and biofilm/adhesion-encoding genes in coagulase-negative staphylococci (CoNS) species recovered from blood culture isolates. Eighty-nine clinical CoNS were confirmed using the VITEK 2 system, and antibiotic susceptibility testing of isolates was conducted using the Kirby-Bauer disk diffusion method against a panel of 20 antibiotics. Isolates were qualitatively screened using the Congo red agar medium. Quantitative assays were performed on microtiter plates, where the absorbances of the solubilised biofilms were recorded as optical densities and quantified. In all, 12.4% of the isolates were strong biofilm formers, 68.5% had moderate biofilm capacity, and 17.9% showed weak capacity. A subset of 18 isolates, mainly methicillin-resistant S. epidermidis, were investigated for adherence-related genes using whole-genome sequencing and bioinformatics analysis. The highest antibiotic resistance rates for strongly adherent isolates were observed against penicillin (100%) and cefoxitin (81.8%), but the isolates showed no resistance to linezolid (0.0%) and tigecycline (0.0%). The icaABC genes involved in biofilm formation were detected in 50% of the screened isolates. Other adherence-related genes, including autolysin gene atl (88.8%), elastin binding protein gene ebp (94.4%), cell wall-associated fibronectin-binding protein gene ebh (66.7%), clumping factor A gene clfA (5.5%), and pili gene ebpC (22.2%) were also found. The insertion sequence IS256, involved in biofilm formation, was found in 10/18 (55.5%) screened isolates. We demonstrate a high prevalence of biofilm-forming coagulase-negative staphylococci associated with various resistance phenotypes and a substantial agreement between the possession of biofilm-associated genes and the biofilm phenotype.

Evaluation of the anti-inflammatory and antioxidant potential of the stem bark extract and some constituents of Aidia genipiflora (DC.) dandy (rubiaceae)

Aidia genipiflora (DC.) Dandy (Rubiaceae) is used to treat various microbial and inflammatory conditions by traditional healers in West African countries. However, there is no information on anti-inflammatory potential of A. genipiflora. This work therefore provides information on the anti-inflammatory and the antioxidant activities of the stem bark extracts and some bioactive constituents of Aidia genipiflora.

Method

The anti-inflammatory activities of the extracts and compounds from A. genipiflora were investigated using the carrageenan-induced footpad oedema assay and the egg albumin denaturation assay. The antioxidant activities of the extract and compounds were investigated using the DPPH radical scavenging assay and the phosphomolybdenum total antioxidant capacity assay. The whole extract of A. genipiflora was also investigated for its acute oral toxicity using the fixed-dose procedure described by the Organization for Economic Cooperation Development guidelines.

Result

The whole extract showed no acute toxicity effect and the LD₅₀ was estimated to be greater than 3000 mg/kg body weight. The whole extract, methanol, and ethyl acetate fractions (30, 100, and 300 mg/kg) showed in vivo anti-inflammatory activity with respective percentage inhibition of oedema of 45.11 ± 3.41, 31.12 ± 3.42 and 29.28 ± 3.58 (p < 0.001) at the highest dose of 300 mg/kg. Diclofenac, used as a reference drug, gave a % inhibition of 48.94 ± 3.58. The compounds isolated from A. genipiflora demonstrated in-vitro anti-inflammatory activity at the IC₅₀ range (16-96 μg/mL) compared to diclofenac (IC₅₀ of 74.48 μg/mL). Oleanonic acid (AG1) and D-mannitol (AG4) further demonstrated in vivo anti-inflammatory activity (ED₅₀ = 20.61 ± 1.29; 23.51 ± 1.26 mg/kg respectively) which was less potent compared to diclofenac (ED₅₀ = 12.50 ± 1.41 mg/kg) in the carrageenan-induced oedema assay. The whole extract, pet. ether, ethyl acetate, and methanol fractions of A. genipiflora exhibited DPPH scavenging activities with respective IC₅₀ of 222.2, 169.7, 121.5, and 40.7 μg/mL. The whole extract of A. genipiflora exhibited considerable total antioxidant capacity with respective values of 248.5 mg/g of ascorbic acid equivalent. All the compounds exhibited low DPPH scavenging activity with IC₅₀ (64-86 μg/mL), compared to ascorbic acid (IC₅₀ of 3.13 ± 1.20 μg/mL). These results highlight the anti-inflammatory and antioxidant activities of Aidia genipiflora stem bark extract and its constituents as evidence to support its traditional uses.

Hypoglycaemic activity of Oleanonic acid, a 3-oxotriterpenoid isolated from Aidia Genipiflora (DC.) Dandy, involves inhibition of carbohydrate metabolic enzymes and promotion of glucose uptake

The present study evaluated the antidiabetic activities of the 70% ethanol stem bark extract of Aidia genipiflora (AGB) and one of its constituents, oleanonic acid in streptozotocin (40 mg/kg)-induced diabetic rats. In vitro assays of glucose uptake and inhibition of carbohydrate metabolizing enzymes were then used to investigate their mechanism(s) of hypoglycaemic action. In silico evaluation of the pharmacokinetic and toxicity properties of the compound was also carried out. Administration of AGB (100-400 mg/kg) and oleanonic acid (15 - 60 mg/kg) resulted in significant reductions (p < 0.001) in the blood glucose and considerable decrease (p < 0.05) in the elevated lipid parameters of the diabetic animals. AGB activity at 200 and 400 mg/kg; and oleanonic acid at 60 mg/kg were comparable to glibenclamide (5 mg/kg). The extract and its isolate strongly inhibited α-glucosidase and α-amylase activity with IC₅₀ values of (10.48 ± 1.39 µg/mL and 14.51 ± 1.26 µg/mL) and (36.52 ± 1.95 µM and 105.84 ± 1.08 µM) respectively. The glucose uptake assays showed that AGB and oleanonic acid exerted both insulin-dependent and independent promotional effect of glucose transport into the periphery by upregulating the expression of PI3K and PPARγ transcripts with a concomitant increase in GLUT-4 transcripts. Although oleanonic acid was predicted to be teratogenic, it was found to be generally non-lethal with favourable pharmacokinetics properties making it suitable for further studies. The study has shown that the stem bark of A. genipiflora is a source of new hypoglycaemic agents and that oleanonic acid possesses hypoglycaemic and anti-hyperlipidaemic activities.

Antinociceptive effect of the hydroethanolic leaf extract of Calotropis procera (Ait) R. Br. (Apocynaceae): Possible involvement of glutamatergic, cytokines, opioidergic and adenosinergic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Pain remains real and still a major problem in clinical medicine which requires new agents with improved efficacy for more therapeutic benefits. Plant sources can serve as a basis for the search for some novel drugs hence the analgesic effects of the hydroethanolic extract of Calotropis procera (CPE) which is widespread in Ghana and other tropical areas and used in folkloric medicine for painful and inflammatory conditions was evaluated.

MATERIALS AND METHODS

The analgesic properties of orally administered CPE at doses of 30, 100, and 300 mg/kg were evaluated in thermal (tail immersion), chemical (acetic acid-writhing, formalin-induced paw licking, glutamate-induced nociception) and mechanical (Randall-Selitto) tests for analgesia. The involvement of tumour necrosis factor-alpha (TNF-α), interleukin 1β (IL 1β), bradykinin, and prostaglandin E₂ (PGE₂) on the analgesic effects of CPE were also evaluated in hypernociception assays measuring mechanical pain thresholds.

RESULTS

The latency of tail withdrawal in the tail immersion test was significantly increased (p = 0.0001) while writhing induced by acetic acid was significantly reduced (p < 0.0001) on treatment with CPE (30-300 mg/kg). The extract also significantly inhibited both phase 1 and phase 2 nociceptive states induced by formalin comparable to morphine (p < 0.0001). Furthermore, the extract significantly attenuated hyper-nociception induced by TNF-α (p < 0.0001), interleukin 1β (p = 0.0102), bradykinin (p < 0.0001), and prostaglandin E₂ (p < 0.0001). Additionally, glutamate-induced paw licking was reduced significantly (p < 0.05). The antinociceptive effects exhibited by CPE (100 mg/kg) in the formalin test was reversed by systemic administration of naloxone (2 mg/kg) and theophylline (5 mg/kg) but not glibenclamide (8 mg/kg), granisetron (2 mg/kg), atropine (3 mg/kg), yohimbine (3 mg/kg, p.o.) nor nifedipine (10 mg/kg).

CONCLUSION

Overall, the hydroethanolic leaf extract of Calotropis procera possesses analgesic properties that is mediated possibly through the glutaminergic, opioidergic, and adenosinergic pathways.

Bioactive constituents with antibacterial, resistance modulation, anti-biofilm formation and efflux pump inhibition properties from Aidia genipiflora stem bark

Background

Antimicrobial resistance is a global health challenge. The involvement of bacterial biofilms and efflux pumps in the development of multidrug resistance (MDR) is well established. Medicinal plants have been proposed as alternatives for combating MDR focusing on their bioactive constituents with resistance modulatory activities. This study was aimed at investigating the stem bark of Aidia genipiflora for bioactive constituents with anti-biofilm, efflux pump inhibition and resistance modulatory activities.

Method

The crude methanol extract was purified by column chromatography and isolated compounds characterized by mass and nuclear magnetic resonance spectrometry. Antibacterial activity was determined by the High-throughput spot culture growth inhibition and the broth micro-dilution assay. The ethidium bromide accumulation assay was used to determine efflux pump inhibition property. Biofilm inhibition was determined in a microplate crystal violet retention assay.

Results

Purification of the ethyl acetate fraction led to the isolation of oleanonic acid (1), 4-hydroxy cinnamic acid docosyl ester (2), β-stigmasterol/β-sitosterol (mixture 3a/b) and D-mannitol (4). The minimum inhibitory concentrations (MICs) ranged from 250 to > 500 μg/mL for extracts and fractions and from 15 to 250 μg/mL for compounds. In the presence of sub-inhibitory concentrations of the compounds, the MIC of amoxicillin against E. coli (20 μg/mL) and P. aeruginosa (320 μg/mL) was reduced by 32 and 10 folds respectively. The whole extract demonstrated anti-biofilm formation and efflux pump inhibition in E. coli, S. aureus and P. aeruginosa. The sterol mixture (3a/b) at concentration of 100 μg/mL caused the highest inhibition (73%) of biofilm formation in S. aureus. Oleanonic acid (1) demonstrated remarkable efflux pump inhibition at MIC of 7.8 μg/mL in E. coli better than the standard drugs verapamil and chlorpromazine.

Conclusion

This study confirms the prospects of A. genipiflora as a source of new antibacterial agents and adjuvants that could interact with some resistance mechanisms in bacteria to enhance the activity of hitherto ineffective antibiotics. “A small portion of the study has been presented in a conference in the form of poster”.

Antimicrobial pentacyclic triterpenes and glycosides from the stem bark of Cussonia bancoensis

The stem bark of Cussonia bancoensis is used traditionally for the treatment of different types of infection and pain. A bioassay guided fractionation of the methanol stem bark extract led to the isolation of five pentacyclic triterpenes and glycosides identified based on spectroscopic data as 23-hydroxyursolic acid (CB1), hederagenin (CB2), 3-O-α-L-arabinopyranosyl-echinocystic acid (CB3), 3-O-α-L-arabinopyranosyl- oleanolic acid (CB4) and 3-O-α-L-arabinopyranosyl-ursolic acid (CB5). CB2 - CB5 are being reported for the first time from this species. The compounds were evaluated for antimicrobial activity against ten microorganisms using the HT-SPOTi method. CB3 demonstrated remarkable antimicrobial activity against S. aureus, S. pyogens, E. faecalis, S. typhi and C. albicans at MICs between 3.12 and 12.5 µg/mL. Among the studied compounds, it was observed that hydroxylation of position C-16 of the oleanane skeleton may enhance antimicrobial activity. This study gives insight into the anti-infective constituents of the stem bark of C. bancoensis and justifies its use in ethnomedicine.[Formula: see text].